Using a hydrogen gas storage tank retaining powdered hydrogen absorbing metal (hereinafter, referred to as “MH”) as a hydrogen supply source of an electric vehicle having a fuel cell has been considered. The hydrogen gas storage tank stores the MH, which stores hydrogen, and supplies hydrogen to the hydrogen supply source by releasing the hydrogen from the MH. As one such type of hydrogen gas storage tank, a hydrogen gas storage tank having a heat medium line extending through a retaining chamber, which retains the MH, has been considered. Heat exchange takes place between the MH and the heat medium.
Also, Patent Document 1 proposes a heat utilization system employing hydrogen absorbing metal, which includes a plurality of stick pipes each configuring a sealed cell retaining hydrogen absorbing metal. Heat medium for outputting cold energy flows outside each of the stick pipes and is cooled through the endothermic effect of the hydrogen absorbing metal. In the heat utilization system, a partition wall dividing a heat medium passage, in which the heat medium flows, into a plurality of portions is arranged in a block case configuring the heat medium passage. The aforementioned cells extend through the partition wall and are arranged in the heat medium passage. The hydrogen absorbing metal absorbs heat from the heat medium when the heat medium flows on the outer surfaces of the cells.
Patent Document 2 proposes a technique in which a single hydrogen gas storage device is configured by stacking a plurality of flat containers, in which hydrogen absorbing metal is received, and fastening and fixing the stacked containers together using tie bolts. Patent Document 3 proposes a heat utilization system employing hydrogen absorbing metal, in which a plurality of stick-like cells accommodating hydrogen absorbing metal in a sealed state are axially clamped together between a first fixing board and a second fixing board and fastened and fixed together using bolts.
The heat utilization system described in Patent Document 1 is not intended to be used as, for example, a hydrogen supply source of an electric vehicle having a fuel cell. The stick-like cells are thus small-sized and light-weighted. Accordingly, in the heat utilization system, the cells are supported only by the partition wall, which is arranged in the block case. However, when the heat utilization system described in Patent Document 1 is employed as, for example, a hydrogen supply source of an electric vehicle having a fuel cell, a large amount of MH must be retained in the cells, and the weight of each cell increases. As a result, the cells cannot be stably fixed if the cells are only supported by the partition wall.
The hydrogen gas storage device described in Patent Document 2 clamps and fixes the stacked containers together between reinforcement boards. In this configuration, the fastening force of the tie bolts is dispersed to the multiple containers. Accordingly, in order to reliably bind the containers together, great fastening force must be applied to the tie bolts.
In the heat utilization system described in Patent Document 3, the multiple cells are clamped and fixed together between the first fixing board and the second fixing board in the axial direction. Accordingly, like the case of Patent Document 2, the binding force applied to the cells by the first fixing board and the second fixing board is dispersed to the cells. It is thus necessary to apply great fastening force to the bolts so as to reliably bind the cells together.    Patent Document 1: Japanese Laid-Open Patent Document No. 2001-208444    Patent Document 2: Japanese Laid-Open Patent Document No. 60-29563    Patent Document 3: Japanese Laid-Open Patent Document No. 2000-320921